115 lines
3.5 KiB
Python
115 lines
3.5 KiB
Python
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#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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Created on Wed Feb 16 12:30:05 2022
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@author: pjoulaud
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"""
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PREM_CARAC = ord('A') - 1
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DER_CARAC = ord('Z')
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#PREM_CARAC = 32
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#DER_CARAC = 126
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#PREM_CARAC = 0x21
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#DER_CARAC = 0x1f0df
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MODULO = DER_CARAC - PREM_CARAC
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def codage_cle_chiffrement(chaine_a_coder, cle):
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"""
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Fonction de codage par substitution polyalphabetique
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Arguments :
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- chaine_a_coder : Message à coder de type str
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- cle : clé de chiffrement de type str
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Retourne :
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- chaine_chiffree : Message codé de type str
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>>> codage_cle_chiffrement("JE TIENS ENFIN LA GAULE", "SCIENCE")
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'CH CNSQX XQONB OF ZDDQS'
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"""
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chaine_chiffree = ""
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i = 0
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for car in chaine_a_coder :
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if car != " ":
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ord_car = ord(car) - PREM_CARAC
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ord_cle = ord(cle[i%len(cle)]) - PREM_CARAC
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sum_ord = ord_car + ord_cle
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#print(f"car : {car} - ord_car : {ord_car} - ord_cle : {ord_cle} - sum_ord : {sum_ord} - ")
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if sum_ord <= MODULO :
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car2 = chr(PREM_CARAC + sum_ord)
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else :
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car2 = chr(PREM_CARAC + sum_ord%MODULO)
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i += 1
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else :
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car2 = car
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chaine_chiffree += car2
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return chaine_chiffree
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def car_to_num(c):
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return ord(c) - PREM_CARAC
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def num_to_car(n):
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if n <= MODULO :
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return chr(PREM_CARAC + n)
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else :
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return chr(PREM_CARAC + n%MODULO)
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def codage_cle_chiffrement2(chaine_a_coder, cle):
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"""
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Fonction de codage par substitution polyalphabetique - 2e version
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Passe par deux fonctions (car_to_num et num_to_car) pour convertir
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de caractères vers valeur numérique et vice-versa.
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Arguments :
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- chaine_a_coder : Message à coder de type str
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- cle : clé de chiffrement de type str
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Retourne :
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- chaine_chiffree : Message codé de type str
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>>> codage_cle_chiffrement2("JE TIENS ENFIN LA GAULE", "SCIENCE")
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'CH CNSQX XQONB OF ZDDQS'
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"""
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chaine_chiffree = ""
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i = 0
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for car in chaine_a_coder :
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if car != " ":
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ord_car = car_to_num(car)
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ord_cle = car_to_num(cle[i%len(cle)])
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sum_ord = ord_car + ord_cle
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#print(f"car : {car} - ord_car : {ord_car} - ord_cle : {ord_cle} - sum_ord : {sum_ord} - ")
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car2 = num_to_car(sum_ord)
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i += 1
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else :
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car2 = car
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chaine_chiffree += car2
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return chaine_chiffree
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def decodage_cle_chiffrement(chaine_codee, cle):
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"""
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Fonction de décodage par substitution polyalphabetique
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Arguments :
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- chaine_codee : Message codé de type str
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- cle : clé de chiffrement de type str
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Retourne :
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- chaine_clair : Message décodé de type str
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>>> decodage_cle_chiffrement(codage_cle_chiffrement("JE TIENS ENFIN LA GAULE", "SCIENCE"), "SCIENCE")
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'JE TIENS ENFIN LA GAULE'
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"""
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chaine_clair = ""
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i = 0
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for car in chaine_codee :
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if car != " ":
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ord_car = ord(car) - PREM_CARAC
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ord_cle = ord(cle[i%len(cle)]) - PREM_CARAC
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sum_ord = ord_car - ord_cle + MODULO
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#print(f"car : {car} - ord_car : {ord_car} - ord_cle : {ord_cle} - sum_ord : {sum_ord} - ")
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if sum_ord <= MODULO :
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car2 = chr(PREM_CARAC + sum_ord)
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else :
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car2 = chr(PREM_CARAC + sum_ord%MODULO)
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i += 1
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else :
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car2 = car
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chaine_clair += car2
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return chaine_clair
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#CORPS DE PROGRAMME
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if __name__=='__main__':
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import doctest
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doctest.testmod()
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